Projectile



Jan. 10, 1950 N. ANDERSON 294949925 PROJECTILE Filed March 28, 1945 3Sheets-Sheet l INVENTOR -fi e/5072 jade/son 15 6 4 ATTORNEY Jan. 10,1950 N. ANDERSON ,4

, PROJECTILE Filed March 28, 1945 3 Sheets-Sheet 2 INVENTOR ATTORNEY1950 N. ANDERSON 2,494,26

PRQJECTILE Filed March 28, 1945 3 Sheets-Sheet 3 INVENTOR Patented Jan.10, 1950 UNITED 2,494,026 PRoJEc'riLE 2 Claims. 1

This invention relates to projectiles including impulse-propelled,gravity-propelled and reaction-propelled, and particularly to means forincreasing the accuracy of such projectiles.

It has been the practice to equip projectiles with stabilizing fins forthe purpose of holding the projectile in alignment with its trajectory,so that it will follow a predicted course as accurately as may be andneither tumble endover-end nor yaw, that is sway from side to side, bothof which erratic actions cause inaccuracies of flight. This has beendone with gravity-propelled projectiles or dropped bombs, withimpulse-propelled projectiles fired from guns, such as mortar shells,and with reaction-propelled projectiles or rockets. All of these typesof projectiles, especially those of low initial velocity, have atendency upon being fired or launched to turn out of alignment withtheir trajectories. While the tail fins or stabilizing fins heretoforeprovided prevent excessive deviation, preventing tumbling and eventuallyreducing or eliminating yawing, their operation has not been aseffective as has been desired. Especially the fins do not exertappreciable restoring torque until the projectile has turned or yawedthru a large angle, and hence they are ineifective to correct slightdeviations. Another disadvantage is overcorrection of the deviationsfrom the desired course. This occurs because the momentum of theprojectile returning to its proper position swings it too far andcarries it out of position again on the other side, due to the fact thatit must travel out of alignment again through a considerable anglebefore the correcting force of the fins becomes effective. This permitsthe pro- .iectile to wobble back and forth during a large portion of itsflight and seriously decreases its accuracy.

One object of my invention is to eliminate these disadvantages andincrease accuracy of flight by providing means which constantly exertson the projectile forces tending to hold the projectile aligned with itstrajectory, even when the deviation is zero. This immediately tends tocorrect deviation.

It has also been common practice to spin projectiles about their axes toefi'ect greater accuracy. This has been attempted by the reaction ofspirally placed fins in the apparent slip stream to spin the projectile.In some cases it has been found that such exposed spinning fins tend toinduce or aggravate yaw and actually decrease the accuracy of theprojectile. Therefore, it is another object of my invention to provideimproved means for spinning that kind of projectile which cannot befired from rifled barrels and to do so without the disadvantage ofexposed spinning fins.

In the accompanying drawings:

Fig. l is a diagrammatic side elevation of a rocket provided with oneform of my invention;

Fig. 2 is an enlarged side elevation of the stabilizing elementindicated in outline in Fig. 1;

Fig. 3 is an enlarged section on the line 3-3 of Fig. 1;

Fig. 4 is a section on the line 4-4 of Fig. 3;

Fig. 5 is a perspective view of a single fin element;

Fig. 6 is an end elevation, as seen from the left of Fig. 2 of amodified form of the invention;

Fig. 7 is a section on the line 'l-'l of Fig. 6;

Fig. 8 is an elevation corresponding to Fig. 2 showing a modified form;

Fig. 9 is a section on line 99 of Fig. 8;

Fig. 10 is an elevation corresponding to Fig. 2 of still another form;and

Fig. 11 is an end elevation corresponding to Fig. 6 of the form of theinvention shown in Fig. 10.

Referring to the drawings, a projectile which may be, for example, arocket or a mortar shell has an explosive head Ill, a shank l l and astabilizing tail I2. The shank lies in or along the apparent slip streamof the projectile. By apparent slip stream is meant the mass of airwhich the projectile pushes aside in its flight and in contact withwhich the projectile passes and which in being passed influences theflight of the projectile. It is that portion or mass of air which, ifthe projectile is considered stationary, apparently moves along theprojectile near or in contact with it so that in its apparent movementit influences the flight of the projectile. The head and shank arestreamlined to offer the smallest practical resistance to flight.

At the tail end of the shank and at a point along which the apparentslip stream passes I provide a symmetrical stabilizing elementprojecting into the apparent slip stream so that it exerts a constantand symmetrical drag or resistance to flight. This may be the surface ofany regular pointed geometrical solid, that is pyramid or cone, pointedto the front, but for ease of manufacture I prefer a conical surface I3.I also prefer a cone whose elements have a low angle to its axis, forexample about 21. This constant drag exerts a constant moment about thenatural center of gyration of the projectile and keeps it true on itscourse and corrects even slight tendency to yaw.

The projectile can be used without any other stabilizing means, but insome instances I may add conventional type radial stabilizing fins I 4projecting from the cone or from the stem, or both. These serve toprovide pockets on the face of the cone and assist the stabilizingaction by preventing the air slipping sidewise ofi the parts of the conethat lie nearest the trajectory in that half of the cone which isexerting drag when in a yaw. This is particularly desirable inconditions in which the initial propelling impulse is great enough andcrooked enough to cause tumbling.

Where such auxiliary stabilizing fins are used, I prefer the novel formof fin shown in Fig. 5. A pair of radial fins l4 jointed at an angle of60 by a conical bridge l and a cylindrical bridge I 6, the bridges beingseparated by an opening H. The conical bridges are secured to the conel3, as by spot welding, at intervals to space the fins equally about thecone. The cylindrical bridges collectively form a cylindrical socket toreceive the shank H which may be secured to the tail assembly in anysuitable manner. The opening I 1 is at the circle where the cylindricalsurface l6 would meet the conical surface [5, and facilitates diestamping of the fin member. The fins may be provided with the usualnotches it for positioning the projectile in the launching device.

When the stabilizing element is used with projectile which can be spunsatisfactorily by exterior fins disposed at an angle to the trajectory,I may incline the fins as shown in M in Fig. 8.

When the projectile is a rocket, the stem Il may form or contain adischarge orifice or nozzle 26 for propelling gases. In such instancesthe hollow inside of the cone forms an expansion chamber 2! continuouswith the discharge orifice and connected to it. Gases flowing from thenozzle expand in the cone and exert more propelling effort on the rocketthan they do without the cone. It has been found that in practice thisadditional effort may not only overcome the drag of the exterior surfaceI3 of the cone but may actually increase the velocity 5% or more.

Where it is desired to have the rocket spin on its axis without usingexterior spinning fins, I provide interior fins 22 on the inside of thecone as shown in Figs. 6 and 7. These are set at any desired angle a",to the elements of the cone for example from 5 to 10 as shown in Fig. 7.Expanding propellant gases leaving the cone and flowing along the finsspin the projectile on its axis.

The invention can also be used with the folding form of fin shown inFigs. 10 and 11. The fins are preferably of the form shown at 23 and aremounted on pivots 24 secured in lugs 25 which are fastened near theouter rim of the cone in any suitable manner. When the projectile isplaced in the gun or launcher the fins are folded against the action ofsprings 26 against the motor casing 23 so as to pass within the barrel3.6. As the projectile leaves the barrel, the springs throw the finsoutward on their pivots, and due to the impulse of the springs and airresistance, or both, they fly into the dotted line position of Fig. 10where they are held by the stop shoulder 29 bearing against the cone l3.

The stabilizing cone can be used either with or without the exteriorstabilizing fins, and either with or without interior spinning finswithin the scope of my invention.

I claim as my invention:

1. In a projectile the combination of a body portion disposed in theapparent slipstream of the projectile when in flight, a drag element onthe rear part of the projectile having a cylindrical portion and aconical portion projecting from the cylindrical portion, and stabilizingfin elements secured to the drag element, each fin element including aportion formed into a part of a cylindrical surface and a part of aconical surface and a pair of integral fins projecting radially fromboth said surfaces.

2. In a projectile the combination of a body portion disposed in theapparent slipstream of the projectile when in flight, a drag element onthe rear part of the projectile having a cylindrical portion and aconical portion projecting from the cylindrical portion, and stabilizingfinele ments secured to the drag element each fin 'ele-- ment includinga portion formed into a part of a cylindrical surface and a part of aconical surface separated from the cylindrical surface and a pair ofintegral fins projecting radially from both said surfaces and connectingthem together.

NELSON ANDERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 646,569 Breath Apr. 3, 1900667,407 Sims et a1 Feb. 5, 1901 1,994,490 Skinner Mar. 19, 1935 FOREIGNPATENTS Number Country Date 41,371 France Oct. 11, 1932

